"So Gleason 4 and above is what matters." Yes I am comparing volume of Gleason 4 in two examples, so definitely with you.

"A larger tumor will mean it has had longer to grow (at whatever rate); not sure if that tells you anything about the tendency to metastasize (except that one wishes it had been found earlier)."
Yes so in one case the tumor is 2.1 cc, and other it is 0.2 cc, so most likely yes the 2.1 cc tumor is older. It doesn't matter how the 3 in there changed over the years, it likely matters how the 4 changed. Since the 4 in the 2.1 cc case is way more gleason 4 it seems concerning, yet it is classified as a less serious cancer for what seems to me just something out of the past categorizations that lacked ability to measure volume even close so before MRI and so on.

I hope people are understanding what I am saying, it does involve some minor math on that Gleason 4. The volume of gleason 4 is way more volume in one but called less serious. I wonder if that should really be the case.